Exploring the complexity of methylphosphonic acid sorption on marine sediments: The influence of organic matter and environmental factors.

This study investigated the sorption characteristics of methylphosphonic acid (MPn) on marine sediments, focusing on the effects of sediment composition and environmental factors. The results indicated that MPn showed good stability on sediment samples and physical process was the main fraction for MPn sorption. Light fraction organic matter (LFOM) significantly enhanced the sorption ability of the sediments. The interactions between minerals and OM in sediments reduced MPn retention. Analysis of organic phosphorus (OP) fractions revealed that the OP sorbed by the sediments mainly existed in exchangeable or loosely sorbed organic phosphorus (Ex-OP) and iron/aluminium-bound organic phosphorus (Fe/Al-OP). Environmental factors influenced the sorption of MPn on sediments. Compared with the artificial seawater (ASW), the sorption ability was stronger in the diluted media. The pH affected the forms of MPn and the surface properties of sediments, significantly increasing MPn sorption under high acidic and alkaline conditions, while the electrostatic repulsion at pH = 8 partially inhibited the sorption. Thermodynamic parameters indicated that the MPn sorption was a spontaneous endothermic process.